1. Field of the Invention
The present invention is generally directed to the field of ramps and inclines, and is more particularly directed to a portable folding wheelchair ramp having an improved joint with increased strength and durability to withstand repeated loads.
2. Description of Related Art
It is often difficult, if not impossible, for people using wheelchairs or walkers to transcend a series of steps, for example, or enter into a vehicle. To assist users in traveling over these type obstacles, ramp structures have been developed to provide an inclined surface on which the user can travel between the two elevations. Insofar as these obstacles can be encountered at a variety of different locations throughout the user""s day, efforts have been made in the art to develop a portable ramp that could be easily transported from one location to another.
In order to make a ramp convenient for transport, it is desirable for the ramp to be relatively compact and lightweight so that it can be easily stored and carried for use. A particularly useful ramp design heretofore developed in the art for these purposes is a foldable ramp comprised of two or more sections which can be folded over one another into an overlapping relationship for carrying. The ramp sections are generally comprised of aluminum sheeting which provides a flat surface on which the wheelchair can move, and aluminum tubing welded or otherwise secured along the bottom surface of the sheeting to provide rib supports. The underlying rib supports of the ramp sections are pivotally hinged together such that the ramp sections can be folded into an overlapping compact position for carrying and unfolded into an extended position for use. In the unfolded position, a portion of the ramp section surfaces formed by the aluminum sheeting overlap at the interface of the two sections to present a relatively uninterrupted surface on which the wheelchair moves.
This prior ramp design is very portable because it can be folded into a compact configuration and because the aluminum materials from which it is made are lightweight. Even though the aluminum materials are lightweight, the use of underlying rib supports generally provides the strength needed to support the load of a wheelchair and its user. However, it has been found that after repeated use, the ramp construction is susceptible to fatigue at the location of the hinge. In particular, the aluminum sheeting tends to buckle and the underlying rib supports tend to break away from the adhesive and/or welds used to secure the supports to the sheeting.
Thus, a need has developed in the art for an improved foldable wheelchair ramp that is less susceptible to failure from material fatigue, yet remains lightweight, compact and provides a relatively smooth platform surface on which the wheelchair can travel.
This need is met by a foldable ramp comprising at least two ramp sections pivotally connected together such that the ramp sections may be folded over one another into an overlapping compact position for carrying, and unfolded into an extended position for use. A keyway joint is provided along the end of the ramp sections such that it connects the two ramp section surfaces when the ramp is in its extended position. The keyway joint operates by having an outer member rotate about an inner member, wherein the inner member limits the rotation of the outer member. It is believed that this type of pivotal connection between the ramp sections is less susceptible to fatigue than the overlapping connections previously used in the art to connect the ramp sections together. Thus, the use of a keyway joint connecting two ramp sections provides a distinct advance in the state of the art wherein the strength of the joint region of the ramp is increased so as to reduce the likelihood of failure from fatigue, while still providing a substantially compact and lightweight ramp for portable use.
In a preferred embodiment, the foldable ramp of the present invention has first and second ramp sections comprised of relatively thin substantially flat ramp surfaces and at least one support member secured to the bottom of each ramp surface. It also has a keyway joint secured in place along one end of each of the ramp surfaces connecting the ramp sections. The keyway joint includes a first rotating member having at least one shoulder and a second rotating member having a rib. The rib and the shoulder are configured to abut in such a manner as to limit the amount of rotation between the members. Preferably, the first rotating member is an internal shaft about which the second rotating member rotates. The internal shaft includes an outwardly extending shoulder that is configured to abut an inwardly extending rib on the second rotating member so as to stop rotation of the second rotating member when it reaches a predefined position. The limited rotation of the keyway joint allows the first and second ramp sections to move between a folded compact position and an open extended position.
In a most preferred embodiment, the keyway joint is comprised of a first collar attached to the first ramp section, a second collar attached to the second ramp section and an inner shaft inserted into the collars and about which the collars rotate. Each of the collars include an inner side wall having a longitudinally extending rib. The inner shaft includes a longitudinally extending pair of shoulders that are configured to abut each of the ribs when the sections are in the extended position so as to limit the amount of rotation of the keyway joint.
In the most preferred embodiment shown in the drawings, the ramp comprises four ramp sections wherein the first and second ramp sections define a left side of the ramp and the third and fourth ramp sections define a right side of the ramp. The left and right sides of the ramp substantially mirror each other, wherein the ramp sections of each side are pivotally connected to one another by a keyway joint as described above. The left and right sides of the ramp are joined together at one or more pivot points so that the sides may be folded over one another into an overlapping compact position, and unfolded into an extended position for use.